This invention relates generally to refrigeration and, more particularly, to the generation and use of refrigeration at a very cold temperature such as is needed to cool, liquefy and/or subcool or densify fluids such as hydrogen and oxygen.
The cooling, liquefaction and/or subcooling or densification of certain gases such as neon, hydrogen or helium requires the generation of very low temperature refrigeration. For example, at atmospheric pressure neon liquefies at 27.1 K, hydrogen liquefies at 20.39K, and helium liquefies at 4.21 K. The generation of such very low temperature refrigeration is very expensive. Inasmuch as the use of fluids such as neon, hydrogen and helium are becoming increasingly important in such fields as energy generation, energy transmission, and electronics, any improvement in systems for the liquefaction of such fluids would be very desirable. Another application is cooling of superconducting systems. Densification of propellants such as hydrogen and oxygen for reusable launch vehicles is another application. It allows larger payloads per space flight and requires subcooling of liquid hydrogen near its triple point which is around 14K.
Accordingly, it is an object of this invention to provide an improved system for generating and providing refrigeration for cooling, liquefying and/or subcooling or densifying fluids such as neon, hydrogen, oxygen or helium.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for providing refrigeration to a product fluid comprising:
(A) compressing pulse tube gas to produce hot compressed pulse tube gas, cooling the hot compressed pulse tube gas, and further cooling the cooled compressed pulse tube gas by direct contact with cold heat transfer media to produce cold pulse tube gas and warmed heat transfer media;
(B) expanding cold pulse tube gas to produce ultra cold pulse tube gas and to produce a gas pressure wave which compresses and heats pulse tube working fluid, and extracting heat from the heated pulse tube working fluid by indirect heat exchange with cooling fluid to produce warmed cooling fluid;
(C) providing refrigeration to product fluid by passing product fluid in indirect heat exchange with the ultra cold pulse tube gas; and
(D) intercepting heat within the heat transfer media by indirect heat exchange with cryogen fluid to produce warmed cryogen fluid.
Another aspect of the invention is:
Apparatus for providing refrigeration to a product fluid comprising:
(A) a regenerator having a regenerator heat exchanger and a regenerator body containing heat transfer media, and means for generating pressurized gas for oscillating flow within the regenerator;
(B) a pulse tube comprising a pulse tube heat exchanger and a pulse tube body, and means for passing cooling fluid to the pulse tube heat exchanger;
(C) means for passing gas between the regenerator body and the pulse tube body, a product fluid heat exchanger employing fluid from the pulse tube, and means for recovering product fluid from the product fluid heat exchanger in a refrigerated condition; and
(D) means for passing cryogen fluid to the regenerator heat exchanger, and means for withdrawing cryogen fluid from the regenerator heat exchanger.
As used herein the term xe2x80x9cliquefyxe2x80x9d means to change a vapor to a liquid and/or to subcool a liquid.
As used herein the term xe2x80x9csubcoolxe2x80x9d means to cool a liquid to be at a temperature lower than the saturation temperature of that liquid for the existing pressure.
As used herein the term xe2x80x9cultra coldxe2x80x9d means having a temperature of 90xc2x0 K. or less.
As used herein the term xe2x80x9cindirect heat exchangexe2x80x9d means the bringing of fluids into heat exchanger relation without any physical contact or intermixing of the fluids with each other.